Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$145.67	8.740%	$158.4016	$158.40	$158.40	$158.40
Purchase #2	$51.89	5.277%	$54.6282	$54.63	$54.65	$54.60
Purchase #3	$70.88	13.223%	$80.2525	$80.25	$80.25	$80.30
Purchase #4	$5.78	9.368%	$6.3215	$6.32	$6.30	$6.30
Purchase #5	$185.50	5.745%	$196.157	$196.16	$196.15	$196.20
Purchase #6	$119.85	10.245%	$132.1286	$132.13	$132.15	$132.10
Purchase #7	$250.71	4.169%	$261.1621	$261.16	$261.15	$261.20
7 purchase totals =	$830.28		$889.0515	$889.05	$889.05	$889.10